Reactive hydroxylated and carboxylated polymers for use as adhesion promoters

ABSTRACT

A polymer complex is disclosed which is the reaction product of one or more polymers having a terminal or pendant hydroxyl group, or a terminal or pendent carboxyl group, or combinations thereof, with at least one metal complex and one alkyl phosphate. This polymer complex acts as an adhesion promotion agent as well as a viscosity stabilizer when formulated in a printing ink or coating.

FIELD OF THE INVENTION

The invention relates to ink compositions containing hydroxylated andcarboxylated polymers that are functionalized with reactive metalcomplexes and alkyl phosphates, which provide adhesion to a wide rangeof substrates without decreasing the viscosity stability of thecomposition.

BACKGROUND OF THE INVENTION

A number of hydroxylated and carboxylated polymers have been found to beuseful in imparting adhesion to a variety of substrates, includingpaper, plastics, metal, and glass. These include polyurethanes,polyurethane-ureas, polyamides, polyesters, polyacrylates,ketone-formaldehyde copolymers, and nitrocellulose that have been usedfor many years in surface coating formulations. Such materials impart anumber of properties to surface coatings, including adhesion, gloss,pigment wetting, surface hardness, and grease resistance.

Typically, substances added to printing inks to promote improvedadhesion to substrates (adhesion promoters) cause the ink to undergo anincrease in viscosity or completely gel on storage. Since inks need tobe of a proper viscosity to perform given their specific application onpress, viscosity increases cause a detrimental effect on the printingprocess. At the very least, inks that increase in viscosity must beadjusted to lower their viscosity, or in some cases, become unusablealtogether. Viscosity stability in inks, with or without the use ofadhesion promoters, is something that is required for properperformance.

In 1955, an article in Chemical and Engineering News reported the use oftitanium chelates, a byproduct of pigment manufacture, for formulatingheat resistant coatings. These compounds also found utility as additivesin nitrocellulose-based printing inks. The most common titanium chelate,titaniumdiacetylacetonate (TiAA), is a reaction product oftetraisopropyltitanate and acetylacetone (AA or 2,4-pentanedione). Thisadditive and variants thereof are used in formulations throughout theprinting ink, paint, and coatings industry. The main disadvantages ofits use is:

A yellowing of the surface it coats. TiAA is a stable complex andcontains, in addition to the two AA groups, two isopropyl groups, whichcan split off under heat and be exchanged by OH groups in a formulation(OH groups of the nitrocellulose e.g.). The TiAA body is susceptible toreacting with aromatic rings, mainly phenolics present in wood rosin andpolyamides forming a deep brownish complex and therefore causesyellowing, especially in white pigmented coating formulations.

Odor. In addition to yellowing, the AA groups can evolve as the surfacecoating dries. These AA groups have a bitter odor that can be sensed atlow concentrations. Therefore formulators of coatings and inks prefer tocompletely avoid AA group containing additives in applications such asfood packaging.

In order to solve the problems described above, in 1985 non-yellowingand low odor adhesion promoters were developed, a description of thesecan be found in U.S. Pat. Nos. 4,659,848 and 4,705,568, and also DE3525910A1. Materials based on these promoters have the disadvantage ofhaving too low a reactivity to, for example, give immediate adhesion ofan ink to a substrate after a short trigger time in a drying oven onpress. In the case of printing inks, this requires the printer to eitherreduce the web speed through the printing press to achieve highertemperatures (reducing productivity) or increasing the effectivetemperature inside the drying oven (increasing cost). In addition, thesehighly reactive compounds often interact prematurely with othercomponents (resins, pigments, additives) in surface coating or inkformulations, resulting in depletion of their adhesion promoting effectand, even more damaging, an unacceptable increase in the viscosity ofthe coating or ink formulation prior to application.

Based upon these facts, there is clearly a need in the art for additivesthat promote better viscosity stability, or better adhesion ontosubstrates, or in the best case, do both with a single additive.

SUMMARY OF THE INVENTION

The present invention is new class of reactive polymers or polymercomplexes that is the reaction product of at least one polymercontaining terminal and/or pendant hydroxyl and/or terminal and/orpendant carboxyl groups, or combinations thereof, with at least onemetal complex and at least one alkyl phosphate.

The present invention provides a viscosity stabilizing and/or anadhesion promoting polymer complex which comprises the reaction productof one or more polymers having a terminal and/or pendant hydroxyl group,or a terminal and/or pendent carboxyl group, and combinations thereof,with at least one metal complex and at least one alkyl phosphate.

The present invention also provides an ink or coating compositioncomprising the reaction product of one or more polymers having aterminal and/or pendant hydroxyl group, or a terminal and/or pendentcarboxyl group, or combinations thereof, with at least one metal complexand at least one alkyl phosphate.

The present invention also provides a method of stabilizing theviscosity of printing ink, paint or coating composition by adding tosaid composition a viscosity stabilizing agent which is the reactionproduct of one or more polymers having a terminal and/or pendanthydroxyl group, or a terminal and/or pendent carboxyl group, orcombinations thereof, with at least one metal complex and at least onealkyl phosphate.

The present invention further provides a method of improving theadhesion performance of an ink or coating composition by adding to saidcomposition an adhesion promoting polymer complex which is the reactionproduct of at least one metal complex with one or more polymers having aterminal and/or pendant hydroxyl group, or a terminal and/or pendentcarboxyl group, or combinations thereof, and at least one metal complexand at least one alkyl phosphate. With the present invention alamination bond strength is achieved at a lower level of metal complex.

The present invention also provides a method of improving the laminationbond strength of an ink or coating composition comprising adding to saidcomposition an agent which is the reaction product of one or morepolymers having a terminal and/or pendant hydroxyl group, or a terminaland/or pendent carboxyl group, or combinations thereof, with at leastone metal complex and at least one alkyl phosphate.

Other objects and advantages of the present invention will becomeapparent from the following description and appended claims.

DETAILED DESCRIPTION OF THE INVENTION

It has now been surprisingly found that the adhesion promotingperformance of hydroxylated and carboxylated polymers in a printing inkor coating can be enhanced by incorporating additional reactivefunctional sites on the polymeric backbone of the polymer therebydeveloping a new class of reactive polymers.

This new class of reactive polymers is the reaction product of at leastone polymer containing terminal and/or pendant hydroxyl and/or terminaland/or pendant carboxyl groups, or combinations thereof, and at leastone metal complex and at least one alkyl phosphate. The new polymerdemonstrates unexpected levels of adhesion at lower levels of metalcomplex when compared to polymeric systems where the hydroxylated orcarboxylated polymer and organometallic or metal containing compoundsare added individually to, for example, a surface coating formulation.Specifically, two distinct beneficial effects have been recognized whenthese new reactive polymers are used in an ink or coating formulation.

As compared to the individual use of metal complexes alone, theviscosity stability in inks and coatings (especially pigmented systems)is enhanced

As compared to the use of the hydroxylated or carboxylated polymersalone, the adhesion performance is enhanced and more rapidly achieved insurface coatings, especially under lower temperature drying conditions.In lamination applications improved performance is demonstrated bysuperior lamination bond strength.

Metal Complex

Preferably, the metal complex is metal orthoester which also preferablyhas the general formula (metal)(OR)₄ in which R represents an alkylgroup which usually contains up to 8 carbon atoms. However, morepreferably the alkyl group has 3 or 4 carbon atoms. It is of coursepossible that mixed alkyl orthometallics may be used such as mixedisopropyl butyl compounds. Most preferably, the metal containingcompound is tetraisopropyltitanate.

Polymer Backbone

Generally speaking, the hydroxylated or carboxylated polymer used toprepare the reactive hydroxylated polymer can be any polymer havingterminal and/or pendant hydroxyl or carboxyl groups. These can be eithernatural or synthetic resins, including (but not limited to)polyurethanes, polyurethane-ureas, polyamides, polyesters,polyacrylates, ketone-formaldehyde copolymers, nitrocellulose. These canbe polymers suitable for both solvent based and water based coatings.

Alkyl Phosphate

The alkyl phosphate is used in the reaction to stabilize the polymercomplex. Preferably, monoalky or dialkyl phosphates are used. Themonoalkyl phosphate used will have the general formula (R₁O)PO(OH)₂ andthe dialkyl phosphate will have the general formula (R₂O)(R₃O)PO(OH),wherein R₁, R₂ and R₃ each independently represents an alkyl group whichcan contain up to 10 carbon atoms but preferably contains no more than 5carbon atoms. Also, preferably R₁, R₂ and R₃ are identical when mixedmonoalkyl and dialkyl phosphates are to be used but this need, notnecessarily be so. Naturally, if desired, the dialkyl phosphate caninclude different alkyl groups. Most preferably, the alkyl phosphateused is amyl acid phosphate.

Example 1 Preparation of Reactive Polymers A. Adhesion-Modified HydroxylFunctional Polyol Resin

In a clean, dry reactor under nitrogen, n-propyl acetate (20.93 grams)was charged along with Degussa Synthetic Resin SK (20.94 grams). Theresulting reaction slurry was stirred and heated to 50-60° C. until allof the resin was dissolved. The reactor temperature was then cooled to25-35° C. Tetraisopropyltitanate (33.91 grams) was added over 15 minutesand the mixture stirred for 15 minutes. The formation of theintermediate reaction product was followed by monitoring changes in theinfrared absorbance of the hydroxyl group at 3400 wavenumbers, where thesignal intensity decreased to 11% of the initial signal upon completionof the reaction. Amyl acid phosphate (24.22 grams) was then added over20 minutes while the reaction temperature was maintained below 60° C.When the addition was complete, the temperature was held at 60° C. for 1hour. Thereafter, the resulting polymer was discharged at a temperatureof 25-35° C. through a 25 micron filter bag and was observed to have theproperties shown below in Table 1.

TABLE 1 Notes on Property: Value: measurements Appearance Clear, yellowliquid Gardener Color 3-5 Brookfield Viscosity 50-150 centipoise 25° C.,#3 spindle @ 60 rpm Percent Solids 58.0-62.0% 100° C. for 15 minutesusing a forced air oven

B. Adhesion-Modified Acid Functional Polyurethane-Urea

In a clean, dry reactor under nitrogen, a solution of an acid functionalpolyurethane-urea in n-propanol and n-propyl acetate (1,000 grams) werecharged. The material was stirred at 25-35° C. Tetraisopropyltitanate (3grams) was added over 15 minutes and the mixture stirred for 15 minutes.The formation of the intermediate reaction product was followed bymonitoring changes in the infrared absorbance of the acid carbonyl groupat 3400 wavenumbers, where the signal intensity decreased to 62% of theinitial signal upon completion of the reaction. Butyl phosphate (2grams) was then added over 20 minutes while the reaction temperature wasmaintained below 60° C. When this addition was complete, the temperaturewas held at 60° C. for 1 hour. Thereafter, the resulting polymer wasdischarged at a temperature of 25-35° C. through a 25 micron filter bag.

C. Adhesion-Modified Acid Functional Polyamide Resin

In a clean, dry reactor under nitrogen, n-propanol (350 grams) wascharged, along with Cognis Versamid 972 (an acid functional polyamideresin) (150 grams). The resulting reaction slurry was stirred and heatedto 50-60° C. until all of the resin dissolved. The reactor temperaturewas then cooled to 25-35° C. Tetraisopropyltitanate (3 grams) was thenadded over 15 minutes and the mixture stirred for 15 minutes. Theformation of the intermediate reaction product was followed bymonitoring changes in the infrared absorbance of the acid carbonyl groupat the appropriate wavenumbers, where the signal intensity/absorptiondecreased by a percentage upon completion of the reaction. Amyl acidphosphate (2 grams) was then added over 20 minutes while the reactiontemperature was maintained below 60° C. When this addition was complete,the temperature was held at 60° C. for 1 hour. Thereafter, the resultingpolymer was discharged at a temperature of 25-35° C. through a 25 micronfilter bag.

D. Adhesion-Modified Hydroxyl Functional Polyester Resin

In a clean, dry reactor under nitrogen, a solution of a hydroxylfunctional branched polyester in n-propanol and n-propyl acetate (1,000grams) were charged. The material was stirred at 25-35° C.Tetraisopropyltitanate (0.6 grams) was then added over 15 minutes andthe mixture stirred for 15 minutes. The formation of the intermediatereaction product was followed by monitoring changes in the infraredabsorbance of the hydroxyl group at 3400 wavenumbers, where the signalintensity decreased to 50% of the initial signal upon completion of thereaction. Butyl phosphate (0.4 grams) was then added over 20 minuteswhile the reaction temperature was maintained below 60° C. When thisaddition was complete, the temperature was held at 60° C. for 1 hour.Thereafter, the resulting polymer was discharged at a temperature of25-35° C. through a 25 micron filter bag.

Example 2 Preparation of Printing Inks and Testing

A printing ink having the composition detailed in Table 2 was preparedusing IA10 adhesion (titanium chelate) promoting agent the synthesis ofwhich is detailed in U.S. Pat. No. 4,659,848, herein incorporated byreference. Additional printing inks were prepared using no adhesionpromoting agent, synthetic resin SK, combination of IA10 and SK or thereaction product of the present invention as described in Example 1.

TABLE 2 INK #1 INK #2 INK #3 INK #4 INK #5 IA10 only SK onlyExperimental IA10 and SK Control (Comparative) (Comparative) (Example 1A) (Comparative) (Comparative) Pigment Red 48:2 52.8 52.8 52.8 52.8 52.8SS nitrocellulose 20.2 20.2 20.2 20.2 20.2 isopropyl acetate 15.4 15.415.4 15.4 15.4 denatured ethanol 133.6 133.6 133.6 133.6 133.6 n-propylacetate 18.0 18.0 18.0 18.0 18.0 Total 240.0 240.0 240.0 240.0 240.0Disperse and add: denatured ethanol 62.6 62.6 62.6 62.6 64.5 n-propylacetate 19.8 19.8 19.8 20.8 20.4 isopropyl alcohol 15.4 15.4 15.4 15.415.8 RS nitrocellulose 15.4 15.4 15.4 15.4 15.8 polyurethane 30.9 30.930.9 30.9 31.8 Citric acid 0.8 0.8 0.8 0.8 0.9 wax compound 3.1 3.1 3.13.1 3.2 slip compound 7.3 7.3 7.3 7.3 7.5 IA10 (titanium 4.8 2.8chelate) Synthetic 4.8 1.0 Resin SK Example 1 4.8 (492-753) 400.0 400.0400.0 400.0 400.0

Viscosity Stability

Ink samples were tested using a #3 Zahn dip-type efflux viscosity cup.Table 3 illustrates the results.

TABLE 3 Aged Viscosity (16 hours @ Ink # Initial Viscosity 48° C.) 1 30seconds 24 seconds 2 25 seconds 20 seconds 3 30 seconds 20 seconds 4 25seconds 22 seconds 5 25 seconds 52 seconds

Adhesion

Test inks 1-5 were reduced to print viscosity (25 seconds @ 25° C. in a#2 Zahn dip-type efflux viscosity cup) and were printed on treatedpolypropylene using a flexographic handproofer. “One Bump” indicates oneapplication of ink. “Two Bumps” indicates two applications of the sameink, one over the other. The results are illustrated in Table 4.

TABLE 4 Air dried Oven dried (no heat applied) (10 seconds @ 80° C. OneTwo One Two Ink # Bump Bumps Bump Bumps 1 2 5 1 1 2 2 5 1 2 3 1 4 1 1 45 4 1 1 5 5 5 1 4 *1 = Best, 5 = Worst

From the above data, the inks of the present invention show superiorviscosity stabilization and tape adhesion properties than commercial andprior art inks.

Example 3

Laminating Inks#6 and 7 were prepared as detailed in Table 5 using IMO(titanium chelate) adhesion promoting agent and the reactive polymerproduct described in Example 1.

TABLE 5 Percent by weight Ink #6 Ink #7 Component: ComparativeExperimental Titanium dioxide 44.1 44.1 SS nitrocellulose solution 2.92.9 polyurethane 31.4 31.4 n-propyl acetate 14.7 14.7 n-propyl alcohol4.9 4.9 IA10 titanium chelate 2 0 Product of Example 1 A 0 2

Viscosity Stability

The inks were tested using a #3 Zahn dip-type efflux viscosity cup. Theresults are illustrated in Table 6.

TABLE 6 Aged viscosity Initial (16 hours Ink # viscosity @ 48° C.) 6 30seconds 60 seconds 7 30 seconds 42 seconds

Adhesion

Inks 6 and 7 were reduced to print viscosity (25 seconds @ 25° C. in a#2 Zahn dip-type efflux viscosity cup) and were printed on treatedpolypropylene using a flexographic handproofer. “One Bump” indicates oneapplication of ink. “Two Bumps” indicates two applications of the sameink, one over the other. The results are illustrated in Table 7.

TABLE 7 Oven dried (10 Ink # seconds @ 80° C.) 6 1 7 1 1 = Best; 5 =worst

From the above data, the inks of the present invention show superior,viscosity stabilizing than inks containing the adhesion promoter IA10.

Lamination Bond Strength

The lamination bond strength of a standard, conventional ink formulatedfrom a commercial urethane/urea polymer was evaluated against an inkmade with the reactive polymer described in Example 1. These results areshown in Table 8.

TABLE 8 Lamination Lamination Bond Bond Strength Strength of of Inkformulated Commercial with reactive polymer Substrate Ink from Example 1A. 48 LBT 49 538 Emblem 434 572 1500 Nylon 50 M30 317 685 SP 65 70 186

From Table 8, it can be seen that the inks formulated with the reactivepolymer from Example 1 have superior lamination bond strength thancommercial inks made with urea/urethane resins.

The invention has been described in terms of preferred embodimentsthereof, but is more broadly applicable as will be understood by thoseskilled in the art. The scope of the invention is only limited by thefollowing claims.

What is claimed is:
 1. A polymer complex comprising the reaction productof: one or more polyurethanes having: a) a terminal or pendent carboxylgroup; or b) a combination of a terminal or pendent carboxyl group and aterminal or pendent hydroxyl group; with at least one metal orthoesterand at least one alkyl phosphate.
 2. The polymer complex of claim 1,wherein said metal orthoester has the formula metal(OR)₄, wherein eachof the four R groups is independently an alkyl group.
 3. The polymercomplex of claim 2, wherein said alkyl group is a C₁ to C₈ alkyl group.4. The polymer complex of claim 2, wherein said alkyl group is a C₃ toC₄ alkyl group.
 5. The polymer complex of claim 1, wherein said metalorthoester is tetraisopropyltitanate.
 6. The polymer complex of claim 1,wherein said alkyl phosphate is a monoalkyl phosphate having the formulaR₁PO(OH)₂ or a dialkylphosphate having the formula (R₂O)(R₃O)PO(OH),wherein each of R₁, R₂ and R₃ is independently an alkyl.
 7. The polymercomplex of claim 6, wherein said alkyl group is a C₁ to C₁₀ alkyl group.8. The polymer complex of claim 6, wherein said alkyl group is a C₁ toC₅ alkyl group.
 9. The polymer complex of claim 1, wherein said alkylphosphate is amyl acid phosphate.
 10. An ink or coating compositioncontaining an adhesion promoting agent comprising the reaction productof: one or more polyurethanes having a) a terminal or pendent carboxylgroup; or b) a combination of a terminal or pendent carboxyl group and aterminal or pendent hydroxyl group; with at least one metal′orthoesterand at least one alkyl phosphate.
 11. The composition of claim 10,wherein said metal orthoester has the formula metal(OR)₄, wherein eachof the four R groups is independently an alkyl group.
 12. Thecomposition of claim 11, wherein said alkyl group is a C₁ to C₈ alkylgroup.
 13. The composition of claim 11, wherein said alkyl group is a C₃to C₄ alkyl group.
 14. The composition of claim 10, wherein said metalorthoester is tetraisopropyltitanate.
 15. The composition of claim 10,wherein said alkyl phosphate is a monoalkyl phosphate having the formulaR₁PO(OH)₂ or a dialkylphosphate having the formula (R₂O)(R₃O)PO(OH),wherein each of R₁, R₂ and R₃ is independently an alkyl.
 16. Thecomposition of claim 15, wherein said alkyl group is a C₁ to C₁₀ alkylgroup.
 17. The composition of claim 15, wherein said alkyl group is a C₁to C₅ alkyl group.
 18. The composition of claim 26, wherein said alkylphosphate is amyl acid phosphate.
 19. A method of improving the adhesionperformance of an ink or coating composition comprising adding to saidcomposition an agent comprising the reaction product of one or morepolyurethanes having a terminal or pendent carboxyl group or acombination of a terminal or pendent carboxyl group and a terminal orpendent hydroxyl group, and at least one metal orthoester and at leastone alkyl phosphate.
 20. The method of claim 19 wherein the viscositystability of an ink or coating composition is also enhanced.
 21. Themethod of claim 19, wherein said metal orthoester has the formulametal(OR)₄, wherein each of the four R groups is independently an alkylgroup.
 22. The method of claim 21, wherein said alkyl group is a C₁ toC₈ alkyl group.
 23. The method of claim 21, wherein said alkyl group isa C₃ to C₄ alkyl group.
 24. The method of claim 19, wherein said metalorthoester is tetraisopropyltitanate.
 25. The method of claim 19,wherein said alkyl phosphate is a monoalkyl phosphate having the formulaR₁PO(OH)₂ or a dialkylphosphate having the formula (R₂O)(R₃O)PO(OH),wherein each of R₁, R₂ and R₃ is independently an alkyl.
 26. The methodof claim 25, wherein said alkyl group is a C₁ to C₁₀ alkyl group. 27.The method of claim 25, wherein said alkyl group is a C₁ to C₅ alkylgroup.
 28. The method of claim 19, wherein said alkyl phosphate is amylacid phosphate.
 29. The method of claim 19 which also promotesstabilizing the viscosity of the ink or coating composition.
 30. Themethod of claim 29, wherein said metal orthoester has the formulametal(OR)₄, wherein each, of the four R groups is independently an alkylgroup.
 31. The method of claim 30, wherein said alkyl group is a C₁ toC₈ alkyl group.
 32. The method of claim 30, wherein said alkyl group isa C₃ to C₄ alkyl group.
 33. The method of claim 29, wherein said metalorthoester is tetraisopropyltitanate.
 34. The method of claim 29,wherein said alkyl phosphate is a monoalkyl phosphate having the formulaR₁PO(OH)₂ or a dialkylphosphate having the formula (R₂O)(R₃O)PO(OH),wherein each of R₁, R₂ and R₃ is independently an alkyl.
 35. The methodof claim 34, wherein said alkyl group is a C₁ to C₁₀ alkyl group. 36.The method of claim 34, wherein said alkyl group is a C₁ to C₅ alkylgroup.
 37. The method of claim 29, wherein said alkyl phosphate is amylacid phosphate.